Neutron Stars as Dark Matter Probes

We examine whether the accretion of dark matter onto neutron stars could ever have any visible external effects. Captured dark matter which subsequently annihilates will heat the neutron stars, although it seems the effect will be too small to heat close neutron stars at an observable rate whilst those at the galactic centre are obscured by dust. Non-annihilating dark matter would accumulate at the centre of the neutron star. In a very dense region of dark matter such as that which may be found at the centre of the galaxy, a neutron star might accrete enough to cause it to collapse within a period of time less than the age of the Universe. We calculate what value of the stable dark matter-nucleon cross section would cause this to occur for a large range of masses.Comment: 8 pages, 7 figure

Effects of voids on the reconstruction of the equation of state of Dark Energy

We quantify the effects of the voids known to exist in the Universe upon the reconstruction of the dark energy equation of state $w$. We show that the effect can start to be comparable with some of the other errors taken into account when analysing supernova data, depending strongly upon the low redshift cut-off used in the sample. For the supernova data alone, the error induced in the reconstruction of $w$ is much larger than the percent level. When the Baryonic Acoustic Oscillations and the CMB data are included in the fit, the effect of the voids upon the determination of $w$ is much lessened, but is not much smaller than some of the other errors taken into consideration when performing such fits.Comment: 6 pages, 4 figure